Electrosensitive recording blank



Oct. 31, 1950 B. L. KLlNE 2,528,005

ELEC'I'ROSENSITIVE RECORDING BLANK Filed May 14, 1948 Q n I 0 E U D O 1.F U

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INVENTOR B.L.KLINE ATTORNEY Patentecl Get. 31, 1956 UNITED STATES PATENTOFFICE ELECTROSENSITIVE RECORDING BLANK Application May 14, 1948, SerialNo. 27,045

1 6 Claims.

This invention relates to an electrosensitive recording blank and moreparticularly to an improved electrosensitive blank On which variouskinds of subject matter may be recorded by means of telegraph facsimileor other types of electrical signals which are applied to selectedelemental areas of the recording blank by means an electrical stylusthat scan the surface of ti blank for applying the signals to selecteda; stherecf.

Facsimile communication systems are now extensively utilized bycommercial telegraph con panics and also by various firms and businesshouses for the transmission and reproduction in facsimile of telegrams,pictures, maps, drawings and other message subject matter. In suchsysthe transmitting blank is scanned either by optical or electricalpickup means, depending upon the character of the transmitting blank,for

' rating the facsimile signals in known man- Reccption of the messagescommonly is ner. effected on dry electrosensitive recording blanks ofthe type disclosed in Kline Patent No. 2,251,742,

issued August 5, 1941. Such a blank comprises base sheet of paper whichis impregnated with a conductive substance, preferably carbon black, sothat the sheet is sufficiently conductive to pass readily the markingcurrents applied by the receiving stylus to the recording blank. Anelectrosensitive marking coating principally composed of leadthiosulphate is applied to the underlying conductive sheet, whichcoating is changed to sulphide in those elemental areas to which themarking currents are applied as the blank is scanned by the recordingstylus during reception of a facsimile message.

The lead-thiosulphate coated blank represented a substantial advanceover the electrolytic and other prior art types of facsimile recordingblanks, and has become a standard blank for use in 'acsimile systems fora variety of types of services; it does, however, have severalundesirahie characteristics which heretofore have been regarded assubstantially unavoidable in this type oi blank. For example, the leadthiosulphate coating produces a gray background instead of white, andwhen titanium dioxide or other Whitening agents are added to the coatingin an effort to produce the desired white background, some loss ofdefinition of the recorded characters is observed and in additionexcessive smoking and an objectionable amount of fumes have resultedduring recording operations. Moreover, a spreading of the marked areasbeyond the proper boundaries of the characters or other subject matteris 2 often encountered when recording on a lead thicsulphate hiank,which results in a smoky fringe similar to a halation about thecharacters except that it is dark instead of light, and causes a'smudgcd appearance or the recorded message.

This appears to be due to a slight charring of the surface of thecoating or to a tarnishing efiect at 1e boundaries of the recordedcharacters, as he einafter set forth. The undesired fringe "fects becomecumulative with facsimile retransmission irom'a receiving blank, and insystems in which it is desirable or necessary to thus repeat a racsimilemessage through one or more relay echoes the cumulative efiects of thespreading or smoky halation prevents the final recorded copy from havinga clean-cut appearance. Further, under certain ecording conditions thespark under the stylus causes the paper blank-,to smolder, whichsmoldering once started may con.- tinue until the entire recording blankis destroyed. C- e of the objects of the invention is to provide arecording blank which is remarkably free from above objections. Theelectrosensitive mark ing coating provides a good white background witha lighter-weight coating than that heretofore possible; the lank recordswith much less smoke and greatly reduced spark at the point of styluscontact, and is substantially non-toxic in operation; the blank is notsubject to smoldering; recording may be effected with lower voltagesthan those required for recording on lead thiosulphate and similarblanks; no smoky fringes about the recorded characters are noticeableand this enables facsimile relay operations to be performed withoutcumulative effects which would produce a smudged appearance ofthemessage, so that the message as recorded in the final station isclean-cut in appearance and acceptable for direct delivery to thecustomer or addressee; and the marking coating is sufficiently white andopaque so that it can successfully be tinted to any desired color evenwhen the coating is applied to a black carbon-bearing conductive paperbase,

While obviating the disadvantages of the prior lead thiosulphate andsimilar blanks, the instant blank retains all of the advantages of theaforer said prior blanks; it may be stored under normal conditions forlong periods of time without any substantial deterioration and is readyfor use at all times; no supplementary development or other treatment ofthe recording blank is necessary apart from the reception of the signalimpulses to record elements during the normal process of recording; itis a dry blank which operates in the absence or" moisture; it is capableof recording at an extremely fast rate and with very sharp definition;is not adversely affected by exposure to light or air; and is adaptedfor use with conventional commercial facsimile recording apparatus of acomparatively simple character.

Other objects and advantages will appear from the following detaileddescription of a preferred embodiment of the invention, taken inconnection with the accompanying drawings, in which Fig. 1 illustratesdiagrammatically a facsimile system embodying transmitting and receivingstations with an intermediate repeating station, the system being of thetype in which a recording blank in accordance with the present inventionis adapted to be used;

Fig. 2 is a perspective view of one form of recording blank embodyingthe invention; and

Fig. 3 is a view, in elevation, of a modified arrangement of therecording blank.

Referring now to Fig. 1 of the drawings, there is shown a facsimiletransmitting station A, a facsimile receiving station C, and anintermediate facsimile relay station B. The transmitter at station A maycomprise either optical or electrical pickup devices, both of which arewell known in the facsimile art; for simplicity an electrical pickupdevice is illustrated. The transmitter comprises a rotatable metalliccylinder or drum I carried by a centrally disposed driving shaft I Iwhich is journaled in frame members [2 and I4. During transmission ofsignals the cylinder is rotated, in the direction indicated by thearrow, by any suitable means such as an electric motor I5, preferably ofthe alternating current synchronous type, which is connected in theillustrative form shown by a driving pulley IE and a belt I! to a drivenpulley I8 keyed to the shaft I I. To prevent slippage, the pulleys havepins thereon which are received in slots in the belts, as indicated.Transmission may be effected in any suitable manner, for example, asdescribed in Kline Patent No. 2,229,091, issued January 21, 1941, inwhich the transmitting blank has conductive characters on anon-conductive background, or as described in my copending application,Serial No. 5,568, filed January 31, 1948, in

which the transmitting blank has non-conductive characters on aconductive background. In such arrangements a scanning electrode orstylus 22, whose point bears on the surface of a blank 2| bearing thecharacters comprising the message, is supported by a traveling carriage23 adapted for longitudinal movement longitudinally along a rotatableshaft 24 screw-threaded throughout the greater part of its length, theshaft being rotated by driving gears 25 and 26 keyed to the shafts I Iand 24, respectively, Whenever the cylinder I 0 is rotated. Thus, thestylus 22 is caused to traverse the cylinder in a longitudinal directionas the cylinder rotates, the pitch of the thread of the shaft 24determining the extent of longitudinal traversal of the stylus duringeach rotation of the cylinder and hence the number of scanning lines perinch. In this manner the stylus point will describe a helical path as itmoves over the surface of the telegraph blank 2I and thus produces ascanning action. The transmitting blank is wrapped once around themetallic cylinder I 0 in the manner shown in the figure and isreleasably secured to the cylinder in any desired manner, as by elasticretaining bands such as shown in Wise et al. Patent 2,255,868, issuedSeptember 16, 1941.

After the blank has been scanned, it is taken off the cylinder andanother blank placed thereon for sending another telegram, means beingprovided whereby the traveling carriage 23 may be manually returned toits starting position. The foregoing method of obtaining a scanningmovement per se is well known, as are various methods of electrically oroptically scanning a given field for producing signals in facsimiletransmission systems, and it is to be understood that any of the knownmethods of producing signals by means of optical or electric scanningdevices suitable for the purpose may be employed. The transmittingapparatus includes a transmitting amplifier 28 which is interconnectedby a com munication circuit LI to the receiving amplifier 30 of theintermediate relay station B. If desired, the transmitted signals mayhave a carrier frequency component introduced by the transformer 21which is connected in a series lead 29 from the transmitting drum I0.

At station B, if the signals incoming over line LI were generated atstation A from a transmitting blank having insulating characters on aconductive background the signals may be inverted by means of a signalinverter 33 so that the message recorded on the receiving blank atstation B will be a positive copy of the message on the transmittingblank 2I. Various of the known types of vacuum tube signal inverters maybe employed. The facsimile repeating equipment at station B,diagrammatically shown within the dotted rectangle 35, may comprisesend-receive apparatus such as disclosed in Wise et a1. Patent No.2,315,361, issued March 30, 1943. A metallic cylinder 36, which carriesan electrosensitive recording blank like the blank BI at station C andmade in accordance with the instant invention, is scanned by anelectrical recording stylus 31 when signals are being received fromstation A. When synchronism of the rotating parts at stations A and B is.properly maintained in any of the various ways known in the art, themessage or image upon the original transmitting blank 2| will bereproduced in facsimile upon the receiving blank on the drum 36. Uponcompletion of the reception of the message, the recording stylus 31 isturned out of engagement with the recording blank and the latter is thenscanned by optical pickup apparatus to relay the message to station C.The retransmitting equipment includes photocells 38 and 39 which providean optical pickup in the retransmitting side, two photocells being usedin order to effect picture reversal and to transmit a positive copy ofthe message in the manner disclosed in Wise Patent No. 2,176,442, issuedOctober 17, 1939.

The signals generated by the optical pickup means pass through atransmitting amplifier 40 and thence over line L2 to the receivingamplifier 42 at station C. The amplified signals are applied to arecording stylus 62. The scanning mechanism of the recorder at station 0is similar to that of the transmitter at station A, and comprises arotatable metallic cylinder or drum carried by a centrally disposeddriving shaft 5I journaled in frame members 52 and 54. During receptionof signals the cylinder is rotated, in the direction indicated by thecurved arrow, by a synchronous motor 55, driving pulley 56, belt 51 anddriven pulley 58 keyed to the shaft 5I The recording stylus 62, whosepoint bears on the surface of the recording blank GI, is carried by atraveling carriage 63 which moves along a threaded shaft 64 rotated bygears 65 and B6 to effect scanning of the blank as the incoming signalsare received. Thus, the recorded blank 6| is a positive facsimile copyof the message on tact bounce or variation in contact resistance;

Applied to the surface of the paper is an adhesive coating or film IIwhich comprises a marking substance in accordance with the presentinvention. The sheet may be made conductive either by impregnation withan electrolyte or by having a finely divided metal power or finelydivided carbon such as carbon black uniformly distributed throughout thepulp from which the paper sheet is rolled, so that signal markingcurrent in the stylus circuit can flow through the sheet to theunderlying metal platen, such as the cylinder shown in Fig. 1, on whichthe sheet is placed during a recording operation. Various examples orsuch electrolytes and conducting powders are disclosed in Kline PatentNo. 2,425,742, issued August 19, 1947. Preferably, finely divided carbonis employed to make the sheet 18 conductive. The thickness of the paperwill depend upon the kind of stock used, for exam ple, the thickness mayvary from .0015 inch for tissue to .003 inch for ticker stock whichcomprises ordinarily manila paper. The degree of conductivity of thesheet 10 is not critical, but

must be sufliciently high to cause the recording stylus current readilyto pass through the sheet. For example, a suitable degree ofconductivity of a carbon impregnated sheet is such that if a metal plateis positioned under the sheet and an electrode whose area of contactsurface is .5 sq. cm. is pressed on the upper surface of the sheet witha pressure of approximately 500 grams, the electrical resistance of thepaper is approximately from 42 to 58 ohms. The resistance of papersimpregnated with electrolytes will be found to be higher and may be ashigh as several times that of the carbon impregnated paper. It will beappreciated by those versed in the facsimile art that the necessaryconductivity of the sheet Ill may vary within considerable limits andyet produce suitable marking eiTects, depending upon various factorssuch as the voltage of the recording stylus current, the thickness ofthe paper 70, the speed at which the recorder is to operate, and

the frequency of the marking current in the stylus circuit whenalternating current is employed.

In accordance with the instant invention, I have discovered that cuprousthiocyanate is especially suitable for use as the marking coating orfilm Hi. There are two copper thiocyanates, the cupric and the cuprous;the cupric is black in color while the cuprous has a very clearbluishwhite color. One method of making cuprous thiocyanate suitable foruse in the blank of the instant invention is to take the commerciallyavailable cupric sulphate or blue vitriol and in solution reduce it tothe cuprous form with a suitable reducing agent, such as sulphurdioxide. cuprous thiocyanate formed in this solution by the addition ofa soluble thiocyanate such as the thiocyanate of sodium, potassium orammonium. Care should be taken to completely reduce the copper solutionto avoid the danger of production of even a very small amount of thecupric form which would decrease the whiteness of the fin ished product.The filtered and washed material is dried and dispersed in a coatingmedium such as a lacquer for application to the conductive base sheet.Commercially it is not the practice to wash the copper thiocyanate withsufficient care to remove all water soluble byroducts of the reactionincluding all traces of acid. Unless this care is taken, the salts oracids will cause deterioration of the coating lacquer and an increase inviscosity or even a gel to make it unusable for commercial coating. Thisextreme care in washing need not be taken if a blank is made byincorporating the copper thiocyanate in the upper surface portion of theblack paper web during the process of manufacture so'that it'becomes anintegral part of the sheet.

The cuprous thiocyanate provides a marking coating that results in agood white background, instead of the grayish background heretoforeobtained in recording blanks, and with a lighterweight coating than thather tofore possible; .45

rain of cuprous thiocyanate coating material per square foot of surfaceis sufficient to provide the same opacity of coating, when applied to ablack carbon bearing paper sheet, as is produced by .85 gram of leadthiosulphate coating material per square foot of surface area, and acoating of .75 gram of cuprous thiocyanate coating material per squarefoot or" surface gives a blank substantially as white as commercialoffice stationery. The recording voltage required in the case of theinstant blank is much lower than that required for lead thiosulphate andsimilar coated blanks, for example, a potential of approximately 160volts normally is required to be impressed upon the stylus for suitablerecording on a lead thiosulphate coated blank, whereas the cuprousthiocyanate blank records with a potential of approximately voltsapplied to the stylus. The blank of the instant invention records withmuch less smoke and greatly reduced spark at the point of the recordingstylus, and is not subject to smoldering regardless of any sparkingwhich may occur, even when recording with direct current at low speeds.Moreover, there is no residual odor in the cuprous thiocyanate blank;such odors have generally been associated with blanks having coatings inwhich chemical change occurs to efiect marking, and these odors in mostcases have proved objectionable. Due to the lower voltage required forpenetrating the marking coating of cuprous thiocyanate, the matchingcircuit impedance for the recording blank may be much lower than thatrequired for lead thiosulphate blanks, and a darker mark is recordedwith less power with the cuprous thiocyanate coating.

When a lead compound coating, such as lead thiosulphate, PbzSOs issubjected to partial decomposition to form lead sulphide, PbS, as inmarking electrosensitive recording blanks, only half of the sulphur inthe molecule is utilized, the other half being discarded. Similarly,when lead thiocyanate, Pb(SCN) 2, is employed as the marking coating inan electrosensitive recording blank, the partial decomposition of thiscompound to form lead sulphide, PbS, results in only half of the sulphurin each molecule being utilized. It is obvious that there is one freesulphur atom liberated for each molecule of lead compound in the coatingwherever a mark is produced. Chemical tests indicate that this wastesulphur in the smoke causes tarnishing of the adjacent lead thiosulphateor lead thiocyanate coating and hence causes darkening in these areaswith consequent smudging around the characters Similarly, tests indicatethat the tendency of a coated blank to smolder may be related to thissame chemical efiect, although positive verification of this isdifiicult and applicant does not wish to be bound as to the precisephenomenon involved. Smolderingis especially serious in the case of lowspeed recording blanks, such as those employed for charts in recordingmeters and cardiographs, since they usually involve a continuous signalwhich affords more opportunity for ignition of the blank. The hazard ofsmoldering is, however, not limited to slow speed recording blanks; italso occurs at times in high speed telegraphic service. For instance,the necessity for fans in hot or humid weather creates drafts whichsometimes cause a smoldering facsimile blank of the prior type to burstinto open flame with the consequent fire hazard. Both lead-thiocyanateand lead-thiosulphate coated blanks show a tendency to smolder andusually will smolder if ignited by the recording spark or any othermeans such as contact with a lighted cigarette. In both of these casesit is believed that the free sulphur resulting from their partialdecomposition to lead sulphide stimulates the smoldering which causesfurther partial decomposition and release of more sulphur in adjacentareas of the sheet, which smoldering may continue until the entire sheetis consumed.

In the case of cuprous thiocyanate, CuSCN, when subjected to partialdecomposition under the action of the marking currents, there is formedeither cuprous sulphide, CuZS, or cupric sulphide, CuS, both of whichare black in color and produce a recorded marking. In the event that theconditions are such that cupric sulphide is formed under the action ofthe marking current, only carbon and nitrogen have been removed from thecuprous thiocyanate molecule, and neither carbon nor nitrogen affectsthe adjacent areas around the characters and hence there is nodiscoloration and smudging. In the event that the conditions are suchthat cuprous sulphide is formed under the action of the markingcurrents, there is only one free sulphur atom liberated for each twomolecules of cuprous thiocyanate and hence the amount of Waste sulphurin the smoke is reduced to an extent as to substantially eliminatesmudging of the adjacent cuprous thiocyanate coating. When alternatingcurrent is used for recording it is a reasonable assumption that thefinal products are both cuprous and cupric sulphides, in which case theamount of free sulphur liberated would be only one-quarter of thatliberated from the foregoing lead compound coatings. If direct currentis employed for marking, it may be expected that either all cupric orall cuprous sulphide will be formed depending upon the polarity of themarking current. In either of the above cases, whether cupric sulphideor cuprous sulphide is the final product, there is substantially nocumulative smudging efiect and clean-cut characters are reproduced inthe final copy even though the subject matter has been retransmittedfrom a like blank one or more times by optical facsimile scanningmethods for relaying a message.

Extensive tests made with cuprous-thiocyanate coated paper have shownthat such blanks do not suport smoldering; in fact, if they are lightedby an open flame so that smoldering is started, the smoldering ceases assoon as the flame is removed or extinguished, and this even though theblanks are subjected to drafts of air at the time they are lighted.Thus, even under adverse conditions, if smoldering should be started itim- 8 mediately ceases due apparently to the chemical behavior of thecuprous thiocyanate upon decomposition thereof.

Due to the lower signaling voltage which may be employed with cuprousthiocyanate, there is also less likelihood of any charring of thecoating around the characters, and this facilitates the production ofclean-cut characters. With a blank in accordance with the instantinvention, it is possible to record a continuous signal and produce asharper line than has heretofore been possible. A coating of cuprousthiocyanate is sufficiently opaque that it may be tinted to any desiredcolor and yet cover the black underlying carbon coating, and it isunnecessary to add whitening agents to the coating to increase itsopacity and produce a white background where desired.

Fig. 3 is a view of a recording blank embodying a conductive paper sheet10 having coatings H and ll of cuprous thiocyanate on opposite sidesthereof, whereby the blank is adapted to record on both sides atdifferent times, respectively, and hence each blank may be used for twodifferent messages, thus materially reducing the cost of using suchrecording blanks. In the use of such a blank, recording usually iseffected by means of alternating current of suitable frequency, for eXample, 2500 cycles, and in this case the conductive paper Ill and theunder coating H which is resting on the metallic cylinder 36 or 50 ofFig. 1, together with the cylinder, act as electrical condenserelements. When the sheet on the recording cylinder is scanned, thestylus 37 or 62 will mark the upper coating H, but the lower coating IIwill remain undisturbed since it is in intimate contact over a largeperipheral area of the cylinder 36 or 50, thus reducing the currentdensity below that required to cause marking of the surface H. Eventhough the coating ll has a very high electrical resistance,displacement currents are passed therethrough at the frequenciesordinarily employed for alternating current recording, due to thecondenser effect produced by the conductive sheet 10 and the cylinder 36or 50 spaced therefrom only by the thickness of the coating ll. After amessage, picture or other record has been produced on the surface H, arecord may be made on the opposite side H merely by reversing the sheetand placing the previously recorded side "H in contact with therecording cylinder 36 or 50.

Inasmuch as the material in the coating H to be reduced or convertedrepresents the load of the electrical marking current, the resistance ofthe recording material should be concentrated in that region. In orderto provide a permanent record, the cuprous thiocyanate may be suspendedin a vehicle or binder of cellulose derivative lacquers, hydrocarbonresins, shellac dissolved in alcohol, or other suitable binder, themarking compound being uniformly distributed in finely divided formthroughout the binder. Since the electrical breakdown strength of theentire coating is to be maintained at a uniform value, with thevariations in reduction or conversion of the marking material beingcontrolled by the intensity of the signaling currents or potentials, thethickness of the coating should be maintained at a substantiallyconstant value throughout the useful area of the record. The coating isapplied as a very thin film, the surface layer preferably being of theorder of .00008 to .00015 of an inch.

As above stated, the white cuprous thiocyanate is reduced or convertedby the application thereto or passage therethrough of the signalingpotentials or currents to a black copper sulphide, this change in colorat the points to which the signaling energy is applied providing a sharpcontrast with the unchanged portions of the coating which have not beenaffected by the signaling potentials or currents. The thickness of thecoating should be just sufiicient to mask the underlying conductive basematerial for supplying a good background for the recorded subjectmatter.

The marking potential applied to the coating by the stylus may be justbelow the marking value so that superimposed signal potentials willprovide the difierential necessary for effective operation. Recordingmay be effected either with direct or alternating currents includingfrequencies raneing into the carrier spectrum. Due to the opacity andwhiteness of the coating it may readily be tinted to produce any desiredcolor of background. For example, the copper thiocyanate may be tintedwith from 1 /2% to 3%, by weight, of a suitable dye to produce any of alarge number of different shades or colors.

In the illustrated embodiment of the invention the entire body of thepaper base 10 is made c0nductive, but if desired only its surface needbe conductive. This may be obtained by coating the sheet ll] with asuitable conducting substance, such as finely divided carbon,incorporated in a suitable binder, for example, synthetic resinscommonly used in lacquers, such as cellulose nitrate, or water solublematerials such as casein, starch and polyvinyl alcohols. Also, a layerof metal foil may be used in lieu of the carbon layer. In such case theelectrode 68 shown in Fig. 1 is placed in contact with the marginal edgeof the conductive surface of the recording blank instead of being incontact with the metallic drum 50, thereby to complete the recordingstylus circuit.

It will be appreciated that other substances or compounds may beembodied in the marking coating in addition to the cuprous thiocyanate,although in general it will be found that the cuprous thiocyanate alonewill be most suitable for recording purposes.

What is claimed is:

1. An electrosensitive recording blank comprising a body portion, saidbody portion having, over the recording surface of the blank, a surfacelayer of a recording medium comprising cuprous thiocyanate in an amountsufficient to produce marking efiects on selectable elemental areas ofsaid recording surface upon application of an electrical signalingpotential to said areas.

2. An electrosensitive recording blank comprisa body portion, said bodyportion having in intimate contact therewith, over the recording surfaceof the blank, a coating of a recording medium comprising cuprousthiocyanate in an amount sufficient, upon application of an electricalsignaling potential to selected elemental areas of the recordingsurface, to form a compound of contrasting appearance with respect toadjoining areas of said surface.

3. An electrosensitive recording blank comprising an electricallyconductive support, said conductive support having in intimate contacttherewith, over the recording surface of the blank, a coating of arecording medium comprising cuprous thiocyanate and a binder, saidcuprous thiocyanate being in sufficient quantity to produce a colorchange in selectable elemental areas of said recording surface whenelectrical signaling potential is applied to said selectable areas ofsaid recording surface, so as to produce a record by the signalingpotential applied thereto.

4. An electrosensitive recording blank comprising an electricallyconducting support, said support containing finely divided carbonuniformly dispersed throughout the body of said support to render thesame conducting, said conductive support having in intimate contacttherewith,

. over the recording surface of the blank, a coating of a recordingmedium comprising cuprous thiocyanate, whereby when electrical signalingpotential is applied to selected elemental areas of said recordingsurface of the blank a color change will occur in said selected areas ofsaid recording surface so as to produce a record by the signalingpotential applied thereto.

5. An electrosensitive recording blank comprising an electricallyconductive fibrous support having a calendered surface, said calenderedsurface of the conducting support having in intimate contact therewith,over the recording surface of the blank, a coating of a recording mediumcomprising cuprous thiocyanate, whereby when an electrical signalingpotential is applied to selected elemental areas of said recordingsurface of the blank a color change will occur in said selected areas ofsaid recording surface so as to produce a record by the signalingpotential applied thereto.

6. An electrosensitive recording blank having at least a surface portionthereof comprising an electrically conductive support formed by finelydivided carbon uniformly dispersed throughout said surface portion torender the same conductme, said conductive surface portion having inintimate contact therewith, over the recording surface of the blank, acoating of a recording medium comprising cuprous thiocyanate applied tosaid surface in the amount of approximately one-half to three-quartersgram per square foot of recording surface area, whereby when electricalsignaling potential is applied to selected elemental areas of saidrecording surface of the blank a color change will occur in saidselected areas of said recording surface so as to produce a record bythe signaling potential applied thereto.

BERNARD L. KLINE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,294,149 Kline et a1. Aug. 25,1942 2,425,742 Kline Aug. 19, 1947 Certificate of Correction Patent No.2,528,005 October 31,1950 BERNARD L. KLINE It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction as follows:

Column 6, line 58, for P10 80 read P63 0 3 and that the said LettersPatent should be read as corrected above, so that the same may conformto the record of the case in the Patent Ofiice. Signed and sealed this23rd day of January, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,528,005 October 31,1950 BERNARDL. KLINE It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows:

Column 6, line 58, for P10 80 read P63 0 3 and that the said LettersPatent should be read as corrected above, so that the same may conformto the record of the case in the Patent Ofiice. Signed and sealed this23rd day of January, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,528,005 October 31,1950 BERNARDL. KLINE It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correctlon asfollows:

Column 6, line 58, for P10 80 read P198 0 and that the said LettersPatent should be read as corrected above, so that the samemay conform tothe record of the case in the Patent Office. Signed and sealed this 23rdday of January, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

1. AN ELECTROSENSITIVE RECORDING BLANK COMPRISING A BODY PORTION, SAIDBODY PORTION HAVING, OVER THE RECORDING SURFACE OF THE BLANK, A SURFACELAYER OF A RECORDING MEDIUM COMPRISING COPROUS THIOCYANATE IN AN AMOUNTSUFFICIENT TO PRODUCE MARKING EFFECTS ON SELECTABLE ELEMENTAL AREAS OFSAID RECORDING SURFACE UPON APPLICATION OF AN ELECTRICAL SIGNALINGPOTENTIAL TO SAID AREAS.